I was actually thinking the reverse. POI bonus effects should be "worse" than they are now, not increased.
The difference in power and levels should be far more devastating than current coding. No one at X level should be killable by someone at X-10. A level 35 offense should not be able to launch 12 attacks and kill a level 45. A level 40 offense in PVP should require (at a minimum), 24 attacks before beating any level 45 defense. A level 35 offense should require at least 50 attacks, if not completely impossible to kill a 45.
This level disparity can also be seen vs. Fortress whereby (after virus), alliances are able to walk fortress at between -10 and -15 levels. Fortress should require -5 to defeat and require nearly 2hrs. Ex; Level 70 fortress should require 24 level 65s to defeat within TWO hours and untouchable otherwise.
Effectively, POI need to carry greater weight and the "ranking" between alliances should also be greater. On some worlds, the "top 5" alliances all receive the same overall bonus.
On older servers, we're seeing level 65 defenses being rolled in a dozen attacks or less from sub 60s.
(old economy) The cost of raising defenses from 57 to 65 is aprox 20T/5T (Cry/Pwr) while the cost of building a level 56 unit (58 offense) offense is only 4T/1T. "Reasonable power generation" at these levels is 500M/hr. Provided the required buildings and associated offenses, we're talking 3+ years to build a 65 defense for 1 base. Meanwhile, attackers can spend 6 months building an offense to wipe out said base.
If I recall the coding, raw costs increase exponentially by 1.2^n while power only increases 1.1^n (n = level). One solution would be to increase defense power by 1.15 (vs 1.1) or test an appropriate option.
While I doubt it's physically possible to make changes in code this deep, the easier solution would be to increase the effect that defensive POIs provide and to increase the disparity between ranks 1 through 10. There is no justification whereby the top 5 POI holders should have the exact same bonus % granted.